Many condensation polymers of formaldehyde and aromatic sulfonic acids have been previously described. U.S. Pat. No. 4,604,404 and U.S. application Ser. Nos. 08/467,725, 08/245,619 and 08/156,443, the entire teachings of which are incorporated by reference herein, disclose the use of such polymers as antiviral agents against the Herpes simplex virus and HIV infection. However, the references do not teach or suggest the use of such polymers in preventing pregnancy.
Spermicidal formulations are popular forms of reversible contraception in the USA (Forrest, J. D. and Fordyce, R. R. Fam. Plann. Perspect. 20:112-118 (1988)). Most intravaginal contraceptive formulations contain the spermicide, nonoxynol-9 (N9) as the active ingredient. These formulations, typically creams, gels, or foams, are generally effective immediately upon application, and can be instilled up to approximately an hour before intercourse (Hatcher, R. A. et al., "Contraceptive Technology, 16th Revised Edition," New York, Irvington Publishers (1994)). Vaginal contraceptive films, such as "VCF" (Apothecus, Inc., Oyster Bay, N.Y.), are more recent introductions to the marketplace, at least in the USA. In contrast to other intravaginal contraceptives, films must be introduced several minutes before intercourse to ensure adequate dissolution and dispersion prior to contact with sperm.
When used alone, spermicides have a failure rate of approximately 21% (that is, typically 21% of couples using these products will experience an accidental pregnancy in the first year of use). Efficacy reportedly improves greatly when spermicides are used in combination with barrier methods, e.g., condoms (Hatcher, R. A. et al., "Contraceptive Technology, 16th Revised Edition," New York, Irvington Publishers (1994)).